I thought that I did, but I didn't.* The reason is that history is written from recorded anecdotes, not from data. This is why the further back you go in history, the less reliable the sources are considered. Seuetonius makes for a fun read, but is it reliable? There's no way to tell.
But for the recent past (say, the last 50 years) we have actual data. What do the data tell us of "Western" vs. "Developing" worlds? Well, they tell us there are no "Western" or "Developing" worlds.
* That's a great book, and you'll be a whole lot smarter after reading it. But as with all history, it's anecdote.
UPDATE 6 January 2013 10:14: Here's a Youtube of Rosling's presentation for those having trouble watching the TED embed.